Maryland Geological Survey 71 



Previous to 1839 no Devonian System was known to geologists. In 

 the Philosophical Magazine for Julj', 1835, Murchison had annnounced 

 his conclusion that beneath the Old Ked Sandstone, then the oldest known 

 series of the Paleozoic era, lay a huge complex of rocks which he named 

 Silurian, after an ancient tribe that inhabited Wales at the time of the 

 Eomans. Above was the great barren series of red rocks followed by the 

 Carboniferous. About the same time, Lonsdale had obtained corals from 

 certain limestones in Devonshire, England, which after careful study he 

 announced to be intenhediate in development between those of the Upper 

 Silurian and the Carboniferous. He thus discovered the Devonian fauna 

 and furnished the " most cogent reason " that led Sedgwick and Murchi- 

 son to delimit a series of rocks that lay above the Silurian and beneath the 

 Carboniferous limestone. In the Philosophical Magazine for April, 1839, 

 these authors together proposed the Devonian System, in a paper entitled : 

 On the Classification of the Older Eocks of Devonshire and Cornwall. 



The discovery of the Devonian System is an interesting one, and the 

 history of its establishment as given by Murchison in his classic work 

 Siluria (edition 1854, pp. 257-8) is here quoted : 



" Devonian rocks {the equivalents of the Old Bed) in Devon and Corn- 

 wall. — The crystalline and slaty condition of most of the stratified de- 

 posits in Devon and Cornwall, and their association with granitic and 

 eruptive rocks and much metalliferous matter, might well induce the 

 earlier geologists to class them as among the very oldest deposits of the 

 British Isles. In truth, the southwestern extremity of England pre- 

 sented apparently no regular sedimentary succession, by which its grey, 

 slaty schists, marble limestones, and silicious sandstones could be con- 

 nected with any one of the British deposits the age of which was well 

 ascertained. The establishment of the Silurian System, and the proofs it 

 afforded of the entire separation of its fossils from those of the Carbonif- 

 erous era, was the first step which led to a right understanding of the age 

 of these deposits. The next was the proof obtained by Professor Sedg- 

 wick and myself, that the ' culm measures ' of Devon were truly of the 

 age of the carboniferous limestone, and that they graduated downwards 

 into some of the slaty rocks of this region. Hence, in the sequel it became 



